Control of Arterial Pressure and Renal Function During Glucocorticoid Excess in Dogs

SUMMARY This study was designed to inrestigate tbe long-term effects of glucocorticoids on the control of mean arterial pressure (MAP) and renal function. Infusion of 10 mg/day of methylprednlsolooe (MP), a glucocorticoid with minimal mineralocorticoid actirity, for 10 days In six intact conscious dogs maintained on a sodium intake of 78 mEq/day resulted in a decrease in MAP from 98 ± 1 to 89 ± 2 mm Hg, a decrease in sodium lothalamate space to 89 ± 2% of control, and a marked Increase in gtomeralar filtration rate (GFR), effective renal plasma flow (ERPF), and urinary sodium excretion. Chronic infusion of MP at doses of 2-800 mg/day in four dogs maintained on low (5 mEq/day) or high sodium intakes (160-223 mEq/day) also caused increases in GFR and ERPF, as well as natriuresis and decreased sodium Iotnalamate space, while causing either no change or a slight reduction in MAP. To determine whether glucocorticoids potentiate the chronic effects of angiotensin II (All) on MAP and renal function, MP was infused in dogs undergoing AH infusion (5 ng/kg/min). During AH hypertension, chronic infusion of 5 or 10 mg/day of MP also resulted in a marked renal vasodilation, natriuresis, and reductions in sodium Iotnalamate space, while causing small reductions in MAP. Thus, we found no evidence that chronic glucocorticoid excess causes hypertension in dogs, or that glucocorticoids potentiate the Mood pressure or renal effects of AH. Instead, glucocorticoids tended to reduce MAP, probably because of chronic renal rasodllation, increased excretion of sodium, and volume depletion.